// 字符串 可以用 '' "" `` 定义
let username: string = "李兵"
 
//数值
let myage: number = 18;
myage = 18.13
myage = -18

// 布尔值 true false
let hasMoney: boolean = false;
hasMoney = true

// undefined null
let unde: undefined = undefined
let nul: null = null;
